This proposal is for the University of California, Berkeley, School of Optometry (UCBSO) to serve as one of five clinical centers in the Vision In Preschoolers (VIP) Study. The VIP Study is a prospective, clinical study designed to develop an effective and efficient battery of screening tests to identify those 3-and 4-year-old Head Start children in need of further vision care for amblyopia, strabismus, and/or significant refractive error, that are the prevalent significant vision disorders of early childhood. To accomplish these goals, a battery of screening tests will be administered to at least 1278 three- and four-year-old children enrolled in Head Start programs in the Berkeley bay area. The battery consists of tests chosen for their design characteristics, validity, and applicability to the preschool population. The battery will include the Massachusetts Visual Acuity Test (MassVAT), which is a modification of the Lea symbols visual acuity test at distance, a Random Dot E (RDE) test of stereopsis, and noncycloplegic autorefraction using the Nikon Retinomax. The battery of tests will be administered at Head Start sites by lay people (Head Start parents) which ensures availability of screeners, utilizes persons with a vested interest in benefitting children from their neighborhoods, and maximizes the applicability of this model to other communities. Each child who fails the screening or is untestable, and a randomly selected subset of children who pass the screening, will undergo a comprehensive eye examination at the UCBSO Clinical Center. The examination will serve as the definitive method, or gold standard, for detection of the target disorders. The sensitivity and specificity for detection of the target disorders will be determined for each of the screening battery tests alone, and in combination. This application documents: a) access of the UCBSO Clinical Center to 1750 children enrolled in Head Start and b) that facilities and personnel are available for conducting vision screenings at the Head Start sites and for conducting gold standard eye examinations. Complete details of the VIP Study rationale, design, and methods are contained in the MOP, which is submitted with the Study Chairperson's application.